Closure unit on flowable product container

ABSTRACT

A closure unit for a container for storing and handling flowable products is made from at least two different thermoplastic materials, the different materials fulfilling different functions. A basic thermoplastic material (A.2) is used for sealing against the container (G.2), and an area made of another different thermoplastic material (B.2,C) is provided to fulfill additional sealing functions, to increase mechanical stability, to have a reduced permeability, and to provide increased elasticity for additional opening and closing and/or absorption characteristics. The closure unit is produced by a multimaterial injection molding process, so that contact surfaces between the different thermoplastic materials can be interconnected by reversible or irreversible positive engagement and/or by more or less pronounced melting into one another. The closure unit is in two parts and comprises a pouring part (1.2) and a closure part (2.2), or is in one part. The two-part closure unit is produced in a single operation in a closed state.

BACKGROUND OF THE INVENTION

The invention is in the field of packing technology and relates to aclosure unit for a container for a flowable product, as well as to aproduction process for said closure unit and a coated cardboardcontainer with a corresponding closure unit.

Containers for flowable products require an opening or a potentialopening through which the product can be removed. It is advantageous if,following the first opening, said opening can be resealed, because onlythen is it possible to handle the container following the first removalof product in the same way as before this has taken place. Thereforemost such containers are provided with a closure unit, which can havethe most varied forms and shapes and which can be made from the mostvaried materials. Known examples for such closure units are stoppersmade from cork and other materials, screw closures made from plastic ormetal, clip or tack closures with ceramic plugs and rubber seals, groundglass stoppers, snap closures made from plastic, etc. Following theinitial opening a container without a closure cannot be tightly sealedagain. The latter e.g. include glass ampules, many beverage containersmade from metal, coated cardboard or plastic.

In the case of containers having a neck, closure units mainly onlyconsist of a closure part, which is mounted on the neck (containerclosed) or is not located thereon (container open), i.e. which can forma reversible, tight connection with the container. In the case ofcontainers without a neck the closure unit mainly consists of a pouringpart (or neck part) and a closure part, the pouring part being connectedin a substantially irreversible, tight manner to the container, whereasthe closure part and the pouring part together form a reversible, tightconnection. In all cases the function of the closure unit is the closingof an opening or potential opening in the container in such a way thatthe opening can be opened by simple manipulations and then resealed. Theclosure unit is so designed that between the closure part and thecontainer (closure unit without pouring part) or between the closurepart and the pouring part (closure unit with pouring part and closurepart) a tight connection can be formed and then removed again withsimple manipulations.

The tight sealing of the container is the main function of the closureunit and substantially determines the design and material thereof.However, in many cases the closure unit must also fulfil otherfunctions. These are e.g. in the case of large openings a minimummechanical support function, in the case of a wine bottle cork a minimumgas permeability, for ease of handling e.g. a permanent connectionbetween the container and the closure part, for safety reasons meanswhich render visible from the outside an initial opening and so on. Forthe case of a closure unit having a closure part and a pouring part, themost important additional function, apart from the in this caseirreversible, tight connection to the container, is the reversible sealbetween the two parts.

Such a multifunctionality of the closure unit makes obvious such a unitmade from several materials, because then for each function it ispossible to use an optimum, suitable material.

Numerous closure units made from several materials are known, e.g. ascrew cap with a sealing insert (functions: stability/positiveengagement, sealing), a cork stopper with a tin cap (functions: sealing,making visible the first opening), a clip closure with a metal clip, theceramic plug and the rubber seal (functions: connection of the containerneck and closure part also in the opened state, mechanical stability andsealing). The disadvantage of all these closure units compared withthose made from a single material is that manufacture is made morecomplicated. Each individual part must be separately manufactured, thenthe individual parts must be assembled and fixed as a unit to thecontainer, or the individual parts must be fitted to the container inseparate steps.

Similar disadvantages and numerous desired improvements, which aredetailed hereinafter, also occur in the case of closure units formedfrom a pouring part and a closure part, particularly those closureunits, such as correspond to the prior art coated cardboard containersfor beverages.

Containers made from coated cardboard for flowable products are inparticular widely used in the food industry to contain drinks orbeverages. There are essentially two different types. They are eitherproduced as a quasi-continuous tube, then filled in one operation,sealed at both sides and then brought into an e.g. rectangular shape byfolding down the corners. Containers produced in this way are completelyfilled with liquid. Prior to opening, by folding up at least one cornerit is necessary to produce a slight vacuum, so that the container can beopened by tearing off a corner region without overflowing. The folded upcorner then serves simultaneously as a spout. It is also possible toproduce the cardboard container empty and open at one end, which is thenfilled and is then closed at said open end by folding and welding. Suchcontainers are not entirely filled with liquid. On such containersconventionally a spout is formed by folding up and at this point thecontainer is opened by tearing. The tearing open of the cardboardcontainer is irreversible. Once the container has been opened, it cannotbe resealed, which limits the use thereof.

In order to obtain less use-limited cardboard containers of this type,various closure units made from different materials have been createdwith the aid of which the container can be resealed following theinitial opening. Such closure units are fitted to the containers priorto filling and namely in the closed state, because they do not have toserve as filling openings. In order that such a closure unit effectivelyimproves the container and extends the possible uses thereof, but doesnot unacceptably increase its price, a number of different requirementsare made. The following list gives the most important requirementsroughly in priority order:

The closure unit must be manufacturable from materials, which aresuitable for contact with foods, ecologically unobjectionable andinexpensive.

The closure unit must be inexpensive to manufacture and fit to thecontainer, i.e. the minimum number of operations should be involved inthe manufacture and fitting, with ideally a single manufacturing stepand a single fitting step.

The closure unit must have a closure part, which can be opened a randomnumber of times and also resealed tightly.

The closure unit must have a pouring part, so that the cardboardcontainer does not have to be folded up for forming a spout.

The closure unit must be such that the container, particularly prior tothe initial opening, is able to withstand without damage roughtransportation.

The closure unit must be openable without undue force and with simplemanipulations, including the first opening.

The closure unit must be hygienic to handle, i.e. its normal handlingshould not involve any engagement in the pouring opening.

The closure unit must be connected as a whole to the container so as toallow easy handling for any normal container use, i.e. there must be nowaste parts at the initial opening and the closure part must bepermanently fixed to the pouring part, but at the same time not impedepouring.

The closure unit must be manufacturable in a large number of differentvariants from the shape and colour standpoints, which satisfy highesthetic demands.

Numerous closure units for such uses are known, which are fitted orfittable to internally coated cardboard containers. Some of these willnow briefly be described and compared with an ideal closure unit withrespect to the above list of requirements.

Such a closure unit e.g. comprises a pouring part and a screw or snaptop, which in the new state are interconnected by a tear or rupturering, all the parts being made from a thermoplastic material. Thepouring part and the top, onto which the tear ring is shaped with apredetermined breaking point, are individually manufactured, fitted toone another, the tear ring and pouring part are welded together and arethen fitted to the container mainly by welding to the inner coating andit must be possible to carry out the welding to the container and of thetear ring and pouring part in a single operating step. Measured againstthe above requirements list this closure unit suffers from thedisadvantage that its manufacture and fitting requires an excessivenumber of working steps, particularly if for hygienic reasons followingthe assembly of the two parts a cleaning stage is required. In addition,the tear ring constitutes a waste part, which exists following theinitial opening. On opening the screw or snap top must be completelyremoved from the pouring part and is then lost. The screw top mustalways be circular, the snap top is advantageously circular, so thatthere are very limited shape possibilities with respect thereto.

Roughly the same disadvantages are encountered in the case of closureunits, which within the pouring part have a sealing diaphragm, whichmust be removed at the initial opening. Such a diaphragm serves as anadditional seal prior to the initial opening. Such a diaphragm canusually only be removed by introducing the fingers into the pouringopening, which does not satisfy the requirement of hygienic handling.

Other closure units with sealing diaphragms in the pouring opening areprovided with perforating or puncturing parts, which must be introducedthrough the diaphragm either manually (hygiene!) or automatically on theinitial unscrewing of the screw top. Such closure units are onlymanufacturable in a large number of steps, but can have as theadditional advantage in the puncturing part a venting channel, whichpermits uninterrupted pouring even when the spout is relatively narrow.

Closure units with snap tops can be moulded in one piece, the pouringpart (with or without an additional sealing diaphragm) being connectedby means of a connecting part, said connecting part also serving as apermanent connection between the two parts. Although such closure unitsfulfil the requirement of one-step manufacture, they must be closedfollowing the latter, which means a further production step. This can beobviated in that a diaphragm is moulded in the pouring part and whichhas an adequate stability to provide an adequately stable closure forthe container prior to the initial opening. In such a case the containercan be made commercially available with an "opened" closure unit. Ifsuch closure units are compared with the requirements list, it can beseen that although manufacture is possible in one step, it requiresextremely complicated moulds and the design of the top is very limitedfrom the material standpoint, although only to a much lesser extent fromthe shape standpoint. The material of the entire closure unit must beeasily tightly connectable, e.g. by welding to the container andnormally to the coating and is consequently defined within narrowlimits. As the cardboard container is usually coated with polyethylene,the complete closure unit is also made from polyethylene and canconsequently not satisfy higher esthetic requirements.

Much the same applies with regards to closure units which largelycomprise a closing diaphragm, which is initially opened along apredetermined breaking point and on which a sealing lip is shaped insuch a way that it can fulfil the sealing function on reclosing. Suchclosure units can be manufactured very inexpensively, but in the newstate are made sensitive by the exposed predetermined breaking point.These closure units can also not satisfy high esthetic demands. Such aclosure unit can also not ensure adequate sealing following initialopening.

Clearly none of the above-described closure units satisfies the completelist of requirements.

SUMMARY OF THE INVENTION

The object of the invention is to so improve multifunctional, one-pieceand two-piece closure units and to provide a process for the productionthereof in such a way that the closure units have the advantages ofclosure units made from several materials, but can be manufactured muchmore simply and also easily fitted to the container. In addition,two-part closure units (with pouring part and closure part),particularly those closure units for coated cardboard containers forbeverages, are to be improved in such a way that they better satisfy themost important requirements of the aforementioned list and also fulfilmore requirements from within said list.

The closure unit of the present invention is made from at least twodifferent thermoplastic materials, which differ with respect to at leastone property. They have interconnected, normally one-piece areas madefrom different materials, which fulfil different functions. The areasmade from the individual materials are interconnected by"interengagement" without connecting means. The interengagement can bemacroscopic, in that the individual parts are so shaped or moulded, thatthey are integrated with one another by positive engagement and/or canbe microscopic in that the surfaces of the different materials aremelted or welded in one another. This interengagement of the materialsis at least partly irreversible, i.e. can only be cancelled out when thematerial areas are at least partly destroyed, but can also be partlyreversible (reversible connection between the pouring part and theclosure part).

The closure unit of the present invention is produced by intermouldingof the different materials (multimaterial injection moulding procedure).The principle of multimaterial injection moulding is to mould a blankfrom a first thermoplastic material, sufficiently cool the same toensure that it is adequately mechanically stable to serve as a mould, atleast partly replace the mould used for moulding the blank and mould thefinished moulding with a further, thermoplastic material, in that theblank partly serves as a mould. This leads to mouldings, which havecontact surfaces between the two materials. In the same way it is alsopossible to mould mouldings from more than two materials.

One advantage of this multimaterial injection moulding procedure isbased on the fact that it permits the moulding of parts integrated intoone another, which otherwise could only be produced by more or lesscomplicated assembly or fitting stages. Thus, parts connected bypositive engagement are moulded, said positive engagement beingreversible or irreversible as a function of the design and elasticity ofthe material.

The other advantage of multimaterial injection moulding is that throughthe choice of the different materials used and by the guidance of themoulding process, it is possible to influence the contact surfacesbetween the materials. As a function of the characteristics of thethermoplastic materials used and the conditions during moulding, thematerial moulded onto an already moulded material will remelt the sameto a varying degree and will mix to a varying degree therewith. Thus, inthe case of corresponding material pairing and/or corresponding guidanceof the moulding process, it is possible to produce contact surfaces withwidely varying characteristics. For example, the two materials can befirmly welded together, but can also only slightly adhere to oneanother, or the two materials can merely be in contact without anyadhesion. Welded contact surfaces are e.g. obtained in that the samematerials, which e.g. differ by their colour, are moulded in oneanother, the strength of the weld being inter alia dependent on thetemperature in the areas of the contact surface during the moulding ofthe second material. Contact surfaces without adhesion are obtained inthat materials which do not mix in the plastic state are moulded on oneanother. If the mixing of the two materials is temperature-dependent,then as a function of the temperatures in the vicinity of the contactsurfaces different adhesion strengths can be obtained during moulding.Different adhesion strengths can also be achieved by the so-calledpolyblend method, in which to the second material is added a variablepercentage of the first material, e.g. 10% for easy adhesion.

The two advantages of the multimaterial injection moulding procedure arefully utilized for producing the closure units according to theinvention. The following boundary conditions apply. The materials usedare primarily determined on the basis of their different functions. Thecontact surfaces between the areas of different materials areirreversibly interconnected throughout on one-piece closure units. Ontwo-piece closure units they are reversibly interconnected where theysimultaneously constitute the separating surfaces of the two parts.Two-piece closure units can be moulded in the closed state using theprocess described.

Around the container opening each closure unit must be tightlyconnectable to the container surface. This is the basic function of theclosure unit and is fulfilled by an area of said unit which is made froma basic material. The characteristics of the basic material areconsequently largely determined by this function. The basic function isreversible for a one-piece closure unit. The basic function isirreversible for a two-piece closure unit, whilst a reversible tightconnection must be provided between the pouring part and the closurepart.

The reversible connection between the pouring part and the closure partis an unavoidable additional function linked with the basic function ofthe closure unit and in the case of the inventive two-piece closure unitis fulfilled by a sealing surface pair, one sealing surface of the pairbeing made from the basic material and the other from the additionalmaterial, the two materials being chosen in such a way that on mouldingon one another they are only sufficiently strongly welded together thatthey can be separated from one another without destruction. The positiveengagement means necessary in order to interconnect in stable manner theclosure part and the pouring part, can either be made reversible by acorresponding shape (e.g. thread) or by a corresponding elasticity (snapclosure) of the participating materials.

The seal between the pouring part and the closure part is ensured by anextremely good matching form of the sealing surface pairs (one sealingsurface serving as a form for the other during manufacture), whichbrings about an adhesion between the two sealing surfaces. In addition,the two participating materials can be so chosen with respect to thethermal expansion coefficient and the process performance with respectto the temperatures, that the intermoulded parts are under a slighttension, which presses together the sealing surfaces. In the new statelimited welding between the two parts can form an additional seal, butthis is lost at the time of initial opening.

As the injection moulding process requires high temperatures and asafter moulding no working step is required, in which any inner surfacesof two-part closure units could come into contact with foreign objects,they satisfy all the hygienic requirements without any special cleaningstage. The reversible positive engagement means between the pouring partand the closure part can be released a random number of times and thenclosed again and for sealing purposes several, e.g. outer and innersealing surfaces can be provided. The pouring and closure parts can,besides areas made from different materials (sealing surface pairs),also have areas made from the same material, which are interconnected bymeans of predetermined breaking points and can therefore serve asadditional sealing means in the new state. Such connection points canalso be constructed as a permanent connection between the closure andpouring parts. Whereas one material forming the part of the closure unitwhich is connected to the container is mainly determined by thisfunction, the second material can be freely selected within wide limits,but always provided that it can be moulded to the first material withoutexcessively coalescing therewith. At a limited extra cost and e.g. fordecorative purposes, further areas from different materials can bemoulded, which only differ e.g. by the colour of the additionalmaterial. Particularly if the closure part is permanently connected tothe pouring part, the possible shapes of the closure part are almostunlimited.

Closure units made by the multimaterial injection moulding process cane.g. be produced from the material pairs polyethylene/polystyrene,polypropylene/styrene-butadiene or polypropylene/polyethylene, all ofwhich are suitable for contact with foods, are ecologicallyunobjectionable and inexpensive.

BRIEF DESCRIPTION OF THE INVENTION

Embodiments of inventive one-part and two-part closure units of thepresent invention are described in conjunction with the followingdrawings, wherein:

FIGS. 1a and 1b are sections through an exemplified, two-part embodimentof the closure unit of the present invention with an additional sealingfunction only, in the open (FIG. 1a) and closed (FIG. 1b) state.

FIG. 2 is a section through another exemplified embodiment with furtheradditional functions.

FIG. 3 is a further exemplified, two-part embodiment of the closure unitin section.

FIG. 4 the embodiment according to FIG. 3 in a part sectional,three-dimensional representation.

FIGS. 5a to 5h show the sequence of the inventive process for theproduction of the exemplified embodiment of the inventive closure unitaccording to FIGS. 3 and 4.

FIG. 6 is a section through an exemplified, one-part embodiment of theclosure unit of the present invention.

FIG. 7 is a section through a further exemplified embodiment.

DETAILED DESCRIPTION

FIGS. 1a and 1b show an exemplified, two-part embodiment of the closureunit according to the invention in the open (FIG. 1a and closed (FIG.1b) state. The closure unit comprises a pouring part 1.1 and a closurepart 2.1, which in the closed state (FIG. 1b) are connected by elasticpositive engagement means. It has areas made from a basic material A.1and areas made from an additional material B.1, which are in each caseconnected. The closure unit can be manufactured by a multimaterialinjection moulding process in the closed state and in one piece.

The pouring part 1.1 is equipped with a closed sealing surface 11.1,which is designed in such a way that around an opening of the containerG.1 it can form a tight connection with the container surface. Thepouring part 1.1 is made from the basic material A.1, which must havethe characteristic that it can form a substantially irreversible, tightconnection with the material of the container surface, e.g. by weldingor gluing. In addition, the basic material A.1 must be compatible withthe product to be stored in the container. The closure part 2.1 is madefrom the additional material B.1, but can also have parts made from thebasic material A.1, as shown in FIGS. 1a and 1b.

The sealing surface pairs fulfilling the reversible sealing functionbetween the pouring part 1.1 and the closure part 2.1 are in each caseformed from the basic material A.1 (sealing surface 12) and theadditional material B.1 (sealing surface 21). These surfaces must beseparable from one another on opening the closure, but without beingdestroyed and this determines one property of the additional materialB.1. The plastic additional material B.1 must only coalesce with theplastic basic material A.1 to such an extent that the release does notinvolve an undue amount of force when opening the closure unit.

If the basic material A.1 extends in continuous areas from the pouringpart 1.1 into the closure part 2.1, then at the potential separationpoint there must be a predetermined breaking point 3.1, where the basicmaterial can be broken with limited force. Such a predetermined breakingpoint has the additional advantage that it forms an additional sealbetween the pouring part and the closure part for as long as said twoparts are still unseparated. If such a predetermined breaking point islocated at a position where it is readily visible, it can also serve asa "seal" and indicate whether the closure unit is new or has alreadybeen opened.

The area made from the basic material A.1 and integrated into theclosure part 2.1 is advantageously connected by irreversible positiveengagement with the area made from the additional material B.1, so thatthe closure part can be removed in one piece from the opening. It canalso fulfil numerous different functions and is correspondinglydesigned. As stated, such functions are e.g. the sealing function in thenew state and the seal function. The basic material A.1 in the closurepart 2.1 can also have a mechanical stability function, so that theadditional material B.1 can be made correspondingly weak. If theadditional material B.1. only has limited compatibility with the productto be stored in the container, the area of the closure part 2.1 madefrom the basic material A.1 can also cover its entire inner surface, sothat at least in the new state the product does not come into contactwith the additional material B.1.

Variants are also conceivable in which the pouring part 1.1 has areasmade from the additional material B.1 and are connected by apredetermined breaking point with the corresponding areas of the closurepart 2.1. It is also possible to have embodiments in which the pouringand closure parts have areas of both materials and in each materialthere are predetermined breaking points. Embodiments are alsoconceivable in which the pouring part is only made from the basicmaterial and the closure part only from the additional material, so thatthen they need have no predetermined breaking points.

An exemplified use for a closure unit according to FIGS. 1a and 1b isfor a bottle for highly viscous liquids, e.g. syrup, which has a pouringpart with improved pouring characteristics compared with the bottle neckand made from polyethylene, as well as a top having an internalpolyethylene coating and two external polystyrene coatings.

FIG. 2 shows an embodiment of the inventive closure unit having furtheradditional functions. Like the embodiment of FIGS. 1a and 1b, itcomprises a pouring part 1.2 and a closure part 2.2. The basic materialA.2 forms areas of the pouring part 1.2, particularly the sealingsurface 11.2, which forms a tight, irreversible connection with thesurface of a container G.2, and areas of the closure part 2.2. Theseareas are connected by a predetermined breaking point 3.2 and have asimilar design to the corresponding areas of the embodiment shown inFIGS. 1a and 1b. The additional material B.2 also forms areas of thepouring part 1.2 and the closure part 2.2.

The pouring part 1.2 has an inner area made from the basic material A.2and an outer area made from the additional material B.2, the outer areae.g. only partly surrounding the inner area and is fixed to the latterby positive engagement means. If e.g. in the vicinity of 4.2 there is apredetermined breaking point, the additional material B.2 fulfils theseal function, because a break at this point is readily visible. Ifthere is no predetermined breaking point at 4.2 and the area iscorrespondingly designed so that the closure unit can also be openedwithout having to separate the pouring and closure parts here, then thispoint fulfils the function of a permanent connection between the neckand closure part.

Two-part closure units according to the prior art with or without apermanent connection between the pouring and closure parts can be madein one operation from one material according to known processes.However, they must be produced in the open state, so that closinginvolves a further operation. The important advantage of the inventiveclosure unit made from two different materials is that it can beproduced in the closed state in one operation, which is particularlyadvantageous in the case of containers, where the opening of the closureunit is not necessary for the filling of the container content (e.g.coated cardboard containers).

The embodiment shown in FIG. 2 can have a further additional functiontaken over from an area in the closure part made from a furtheradditional material C. The latter can e.g. be so porous that although ittightly seals the container with respect to its content, it allows a gasexchange between the interior of the container and the external air, sothat the container content can age in controlled manner. The additionalmaterial can also be so elastic that it can e.g. be perforated by ahollow needle and the perforation can reseal after the removal of theneedle. Therefore the area made from the further additional material Cfulfils an additional removal or addition function, which can be carriedout with the closure unit closed. It is also conceivable for the areamade from the further additional material C to be sealed with respect tothe outside by the additional material B.2 and for the furtheradditional material C to have absorption characteristics. In areas ofadditional material C, it is possible to store a material by absorptionwhich can have a controlled interaction with the container content.Examples of such materials are flavouring agents, vitamins orpreservatives.

The design of the area from the further additional material C is on theone hand dependent on its function and on the other on the materialpairing of the materials A.2 or B.2 and C. If they can be sufficientlystrongly welded in the case of intermoulding in the micro and/or macrorange, simple shaping is possible, but if they cannot be welded, asshown in the drawing, then positive engagement means are required.

It is obviously also possible to have embodiments of the inventiveclosure unit with only some of the additional functions described inconjunction with FIG. 2, as well as those having further additionalfunctions.

FIGS. 3 and 4 show in section (FIG. 3) and in part sectional view (FIG.4) another exemplified, two-part embodiment of the inventive closureunit in detail. It is once again a unit formed from a basic material A.3and an additional material B.3, which is particularly suitable for useon a coated cardboard container and whose pouring part 1.3 and closurepart 2.3 have areas from both materials A.3 and B.3.

The pouring part is designed as a substantially tubular part, which mayor may not be circular, on whose end remote from the closure part isshaped a flange-like connecting ring 31, which is e.g. welded to theinner coating of the container G.3. The connecting ring 31 and also thepouring tube 32 of the pouring part 1.3 are made from the basic materialA.3. In order that the inner coating of the container G.3 and theconnecting ring 31 can be easily welded together, e.g. for apolyethylene-internally coated container, polyethylene is advantageouslychosen as the basic material A.3. A bead 33 is provided as a positiveengagement means on the outer end of the pouring tube 32 facing theclosure part 2.3. The area made from the basic material A.3 extends intothe closure part 2.3 and namely via the entire opening of the pouringtube 32, a predetermined breaking point 3.3 being provided around thelatter.

The closure part 2.3 is made from both materials (A.3, B.3), an innerarea 34 is made from the basic material A.3, an outer area 35surrounding the inner area on both sides is made from the additionalmaterial B.3. Both areas are provided with openings which, as will bedescribed hereinafter, are mainly a result of the moulding process. Theclosure part has a channel or groove corresponding to the bead 33. Thearea made from the additional material B.3 on the outside of the pouringtube extends in the form of a web 36 to below the container wall, whereit is positively secured between the container G.3 and the connectingring 31. The web 36 is e.g. used as a permanent connection between theclosure part and the pouring part.

The sealing surface pairs between the pouring part 1.3 and the closurepart 2.3 according to FIGS. 3 and 4 and which can be arranged on theoutside and/or inside of the pouring tube 32, in each case comprise asealing surface made from the basic material A.3 on the pouring side anda sealing surface made from the additional material B.3 on the closureside. In the case of a given basic material A.3 (connection to thecontainer), the additional material B.3 is also determined by therequirement that it must be possible to weld together the sealingsurface pairs, without any excessive coalescing of the materials. A weldbetween the sealing surfaces, whose separation does not excessivelyincrease the force required for opening the closure unit can beaccepted, or may even be desirable as an additional seal for the newstate. For good sealing a limited tension between the pouring part 1.3and the closure part 2.3 is also desired through which the sealingsurface pairs are pressed against one another. Such a tension can e.g.be achieved in that the two materials are so chosen that the additionalmaterial B.3 has a higher thermal expansion coefficient and the basicmaterial A.3 a lower thermal expansion coefficient, so that on coolingthe additional material B.3 shrinks more and consequently the outersealing surface pairs are pressed onto one another in the vicinity ofthe bead 33. If the thermal expansion coefficient of the basic materialA.3 is higher than that of the additional material B.3, the pouring tube32 will shrink more than the closure part and will exert a pressure inareas of the inner sealing surface pairs. These tensions desired for agood sealing action can be achieved not only through a correspondingmaterial selection, but also by a corresponding guidance of the mouldingprocess, in which the two materials do not have the same temperatureswhen moulded on one another, as well as by corresponding shaping of theareas of the different materials.

The closure unit according to FIGS. 3 and 4 is manufactured in theclosed state by a two-stage injection moulding process, which will bedescribed in greater detail in conjunction with FIGS. 5a to 5h. At thetime of initial opening, i.e. on raising the closure part 2.3 from thepouring part 1.3, the area of the basic material A.3 breaks along thepredetermined breaking point 3.3 and is divided into two parts, theadditional seal formed by the area of the basic material A.3 when thecontainer is new and extending from the pouring part 1.3 into theclosure part 2.3 is destroyed. The area made from the additionalmaterial B.3 is deformed in areas of the web 36, but remains in tact, sothat the pouring part 1.3 and the closure part 2.3 remain permanentlyinterconnected.

The following variants of the embodiment shown in FIGS. 3 and 4 andwhich have in part already been mentioned in conjunction with FIGS. 1and 2 are conceivable.

The pouring tube 32 can have a non-circular pouring opening,particularly if between the closure part and the pouring part there is apermanent connection and therefore, even without special attention, theclosure part can be placed on an opening having a less pronouncedsymmetry.

The area made from the basic material A.3 can be limited to the pouringpart, so that there is no need for the additional seal by thepredetermined breaking point 3.3 in the new state.

The area made from the additional material B.3 can also be restricted tothe closure part 2.3, i.e. the web 36 can be omitted, so that thepermanent connection between the pouring and closure parts is obviated.

The area of the additional material B.3 extending into the pouring part1.3 can be anchored by positive engagement means to the area of thebasic material A.3 without coming into contact with the container G.3.

The closure unit, particularly the closure part 1.3, can have areas of athird material, which can fulfil a further function or serve decorativepurposes (cf. also FIG. 2).

Instead of being in three-layer form (B/A/B), the closure part need onlybe in two-layer form (B/A or A/B).

The connecting ring 31 can be connected to the outer surface of anexternally coated container (cf. also FIG. 1).

FIGS. 5a to 5h show an example of an manufacturing process illustratingthe production sequence for the embodiment of the closure unit accordingto the invention, as described in conjunction with FIGS. 3 and 4. Thedrawings show in time-succeeding manner the following states of themoulded product and moulding means in section.

State 5a shows the moulding means for moulding the blank from the basicmaterial A.3. The moulding means are parts 51,52.1,52.2,53, 54.1,54.2 ofa mould which can be moved relative to one another and which havespacing means, e.g. rods 55 movable relative to a means 51 and ejectingmeans (not visible in this state), together with a moulding nozzle 56.

State 5b is the moulding state of the moulding means for moulding theblank e.g. from the basic material G.3. In this state the means form aclosed mould, which is obtained in that means 51,52.1 and 52.2 remainstationary, whereas means 53,54.1 and 54.2 move (arrows).

State 5c is the state during the actual moulding of the blank 50 fromthe basic material A.3 and which is injected by the moulding nozzle 56.

States 5d,5e and 5f show the replacement of the mould after moulding theblank. Moulding means 53,54.1 and 54.2 are removed (state 5d, arrows)and are replaced by means 63,64.1 and 64.2 (state 5f, arrows). Inaddition, the means 51 is moved relative to the spacing means 55 in sucha way that between the blank 50 and the means 51 a new moulding cavityis obtained and the blank is kept by the spacing means 55 in itsoriginal moulding position. The blank 50, spacing means 55 and means 51(in the new position), 52.1, 52.2 (in the original position), 63,64.1and 64.2 now form a closed mould for the finished moulded product.

State 5g is the state during the effective moulding of a secondmaterial, e.g. the additional material B.3, which is supplied by themoulding nozzle 66.

State 5h shows the moving away of the means 63,64.1 and 64.2 (largearrows) and the raising of the moulding 60 from the means 51,52.1 and52.2 by the ejecting means 67.1 and 67.2 (small arrows).

The complete moulding process is e.g. performed at two mouldinglocations (one for the states 5a to 5d and the other for the states 5eto 5h), between which oscillate or travel the moulding means 51,52.1 and52.2 (in one direction with the blank). The cycle time, i.e. the timerequired to manufacture a closure unit is then the time required forpassing through the states 5a to 5d or 5e to 5h. The cycle time can befurther reduced by several moulding locations functioning in parallel.

Part of the moulding of the blank and the finished moulding is based onthe moulding procedure used. If additional material is to be mouldedround both sides of the blank, it must have corresponding openings.Additional material cannot be moulded entirely round the blank, becausethe latter must be held in the moulding position for the second mouldingstage by means (moulding means 52.1 and 52.2, spacing means 55).

In order to keep the costs for the multimaterial injection mouldingprocess to within acceptable limits, it is important for the mouldingmeans not to have an excessively complicated shape and for the cycletime, i.e. that required for a moulding cycle from state 5a to state 5dis as short as possible. The cycle time can be kept short if it isensured that the parts to be moulded are so thin that they can besufficiently cooled during the time which must be expended for movingthe means, so as to be sufficiently stable for the next state. This isinter alia achieved in that parts which must have a specific thicknessfor a specific mechanical strength are moulded from both materials intwo or three layers. The closure part of the embodiment described inconjunction with FIGS. 3 and 4 is designed on this basis.

FIG. 6 shows a one-part embodiment of the inventive closure unit, whichhas no additional sealing function as a result of its one-part nature.It is a plug made from two materials, the basic material A.6 fulfillingthe sealing function, which is in this case reversible, with respect tothe container surface (G.6), whilst the additional material D has one ormore additional functions, which in the represented case can e.g. be themechanical strength or an esthetic function. The contact surfacesbetween the two materials A.6 and D must be irreversibly connected, i.e.the material pairing must be chosen in such a way that the surfaces arewelded together on intermoulding and/or the shape thereof is to be soselected that they are positively interconnected. The basic material A.6is also in this case determined by its sealability with respect to thecontainer surface and by its compatibility with the container content.The additional material D is determined by the additional function andby the requirements concerning the material pairing of the basic andadditional materials.

A one-part, inventive closure unit can also be in the form of a screw orsnap top.

FIG. 7 shows a further, one-part embodiment of the inventive closureunit. It is an embodiment in which the additional material E can assumeadditional functions according to the additional material C of theembodiment of FIG. 2. In such a plug, once again the sealing functionwith respect to the container surface (G.7) is fulfilled by the basicmaterial A.7 and the additional functions such as mechanical stability,porosity and/or absorptivity are fulfilled by the additional material E.

I claim:
 1. A closure unit made from thermoplastic material for closinga container for the handling and storing of a flowable product, theclosure unit comprising:a first continuous area made from a basicthermoplastic material; and at least a second continuous area made fromanother thermoplastic material which differs from the basicthermoplastic material in at least one property; said first continuousarea having a closed sealing surface which is connectable around acontainer opening in a tight sealing manner with respect to thecontainer material; said first and second continuous areas being coupledto one another such that they are separable only as a result of an atleast partial destruction of at least one of said first and secondcontinuous areas; a pouring part which comprises at least a portion ofsaid first continuous area, and which is at least partly made from saidbasic thermoplastic material; and a closure part for closing saidpouring part, said closure part comprising at least a portion of saidsecond continuous area, and said closure part being at least partly madefrom said another thermoplastic material; said basic thermoplasticmaterial and said another thermoplastic material having respectiveproperties such that they can be molded onto one another withoutcoalescing; at least one of said pouring part and said closure parthaving positive engagement means for engaging the other of said pouringpart and closure part; and said pouring part having at least one sealingsurface made from said basic thermoplastic material, and said closurepart having at least one sealing surface made from said anotherthermoplastic material, said sealing surfaces of said pouring part andsaid closure part, in a closed state of the closure unit, resting on oneanother and together with said positive engagement means forming areversible, tight connection of said closure part to said pouring part.2. The closure unit of claim 1, wherein said first continuous area madefrom said basic thermoplastic material extends both into said closurepart and into said pouring part.
 3. The closure unit of claim 2 whereinsaid first continuous area, which extends both into said closure partand into said pouring part, has at least one predetermined breakingpoint at a transition from said closure part into said pouring part. 4.The closure unit of claim 3, wherein said at least one predeterminedbreaking point is at least partly located around said pouring opening ofthe container.
 5. The closure unit of any one of claims 1-4,wherein:said positive engagement means fixes said closure part to saidpouring part; and said positive engagement means comprises at least onebead on an outside portion of said pouring part and a correspondingchannel on said closure part.
 6. The closure unit of any one of claims1-4, wherein:said first continuous area, made from said basicthermoplastic material, forms a connecting ring at an end of saidpouring part which is remote from said closure part; said basicthermoplastic material is a thermoplastic material with which acardboard container is coated; and said connecting ring has a surfacefacing said closure part which is welded to the coating of the cardboardcontainer.
 7. The closure unit of any one of claims 1-4, wherein saidbasic and another thermoplastic materials have respective differentthermal expansion coefficients.
 8. The closure unit of any one of claims1-4, wherein said basic and another thermoplastic materials arepolyethylene and polystyrene, respectively.
 9. The closure unit of anyone of claims 1-4, wherein said basic and another thermoplasticmaterials are polypropylene and styrene-butadiene, respectively.
 10. Theclosure unit of any one of claims 1-4, wherein said basic and anotherthermoplastic materials are polypropylene and polyethylene,respectively.
 11. The closure unit of any one of claims 1-4, whereinsaid another thermoplastic material contains a small percentage of saidbasic thermoplastic material.
 12. The closure unit of any one of claims1-4, wherein at least one area of a material extending over said pouringpart and said closure part remains cohesive on removing said closurepart from said pouring part.
 13. The closure unit of any one of claims1-4, further comprising additional areas of at least one of said closurepart and said pouring part made from a further thermoplastic materialwhich is different from both of said basic and another thermoplasticmaterials.
 14. The closure unit of claim 13, wherein said additionalareas made from said further thermoplastic material are connected by atleast one of positive engagement and contact surfaces melted into oneanother in an irreversible manner to at least one of said closure partand said pouring part.
 15. A process for making a closure unit accordingto claim 1, comprising:molding a blank corresponding to said firstcontinuous area from said basic thermoplastic material in a mold;replacing at least part of the mold, and thereafter molding the secondcontinuous area from said another thermoplastic material in said mold;said blank forming at least part of the mold for molding said secondcontinuous area from said second thermoplastic material, said secondcontinuous area being connected to said blank during said molding ofsaid second continuous area.
 16. In a container made from coatedcardboard for containing a flowable product, the container having aclosure unit made from thermoplastic material, and the closure unitbeing fixable on the container, the improvement wherein the closure unitcomprises:a first continuous area made from a basic thermoplasticmaterial; at least one second continuous area made from anotherthermoplastic material; said basic thermoplastic material and saidanother thermoplastic material differing from each other in at least oneproperty; the first continuous area having a closed sealing surfacewhich is connectable around a container opening in tight manner with thecontainer material; the first and second continuous areas beingseparable only as a result of at least partial destruction of at leastone of said first and second continuous areas; a pouring part whichcomprises at least a portion of said first continuous area, and which isat least partly made from said basic thermoplastic material; and aclosure part fur closing said pouring part, said closure part comprisingat least a portion of said second continuous area, and said closure partbeing at least partly made from said another thermoplastic material;said basic thermoplastic material and said another thermoplasticmaterial having respective properties such that they can be molded ontoone another without coalescing; at least one of said pouring part andsaid closure part having positive engagement means for engaging theother of said pouring part and closure part; and said pouring parthaving at least one sealing surface made from said basic thermoplasticmaterial, and said closure part having at least one sealing surface madefrom said another thermoplastic material, said sealing surfaces of saidpouring part and said closure part, in a closed state of the closureunit, resting on one another and together with said positive engagementmeans forming a reversible, tight connection of said closure part tosaid pouring part.